The present invention relates to a heat cutting/bonding blade apparatus for heat-cutting two or more sheets of thermoplastic resin, particularly non woven cloth sheets of a thermoplastic resin, laminated one on another, and thermally welding the cut edges of these sheets. The invention also is concerned with a heat bonding apparatus which can heat-bond superposed sheets of thermoplastic resin without cutting them.
A known heat cutting/welding blade, capable of thermally heat-cutting superposed non-woven cloth sheets of a thermoplastic resin and heat-bonding the cut edges of the sheets, employs an isosceles triangular cutting edge portion which is heated by, for example, an electrical heating coil. The cutting edge is advanced into the layers of the thermoplastic resin sheets while cutting these sheets and thermally fusing the cut edges so as to heat-bond the superposed sheets.
On the other hand, a heat-bond blade has been known which is capable of pressing an end surface of a heated plate to sheets to be welded so as to fuse and bond both sheets without cutting them. This type of welding blade apparatus can perform heat-seal of non-woven cloth sheets formed by film-laminate process.
A heat-bonding apparatus having the following features also has been known for heat-bonding sheets without cutting. This known apparatus is intended for use in forming a sack by welding non-woven cloth sheets formed by thermoplastic resin. As shown in FIG. 21, this known apparatus employs a disk-shaped heat-bonding blade 40 which is knurled at its peripheral surface as at 41. This heat-bonding blade 40 is adapted for cooperating with an anvil roll 42 having a similar structure. In use, the heat-bonding blade 40 is heated by means of, for example, an electric heater coil. The welding blade 40 is then made to roll on the sheets of the thermoplastic resin so that the superposed sheets are heated and fused so as to be welded together.
This known heat-bonding blade apparatus has the following problems. Namely, when this known apparatus is used for the purpose of melt-cutting and bonding of non-woven cloth sheets of polypropylene, the bonded portion usually exhibits inferior appearance and low bonding strength. Namely, the processing conditions for obtaining both good appearance and high bonding strength are extremely limited, and only well skilled persons could conduct the processing under such restricted conditions. In addition, the production efficiency was extremely low.
In order to avoid this problem, it has been a common measure to laminate a film having high bondability, e.g., a polyethylene film, to the non-woven cloth of the polypropylene sheet, so as to enable an easy cutting and sealing. This countermeasure is quite uneconomical.
Another problem encountered with the conventional heat-bonding blade apparatus is that the bonding strength is insufficient when three or more layers are superposed and heat-sealed, though this known apparatus provides appreciable cutting and bonding effect when used for a pair of sheets. This problem is serious particularly when a non-woven cloth sheet is used as one of the constituent elements of the laminated sheet structure.
Furthermore, the known heat-bonding blade apparatus could not provide acceptable appearance and bonding strength when used for heat-bonding a pair of sheets of non-woven cloths which have no film laminated thereon.